Second harmonic of nonlinear magnetoimpedance in amorphous magnetic wires with helical anisotropy

Abstract

The axial magnetic field dependence of the second harmonic of giant magnetoimpedance in Co-rich amorphous wires with helical anisotropy has been measured to high field resolution in the current amplitude range of 2–14 mArms and frequency range of 200 kHz–3 MHz. We have found that the intensity of the inner peaks of the four-peak structure increases with current amplitude until a threshold value, and then begins to decrease without changing position, whereas the outer peaks decrease monotonically and move to higher field. When frequency is increased from 200 kHz to about 2 MHz, all of the four peaks increase in height and move to higher field. Beyond 2 MHz, all of the peaks move to lower field; the intensity of the inner peaks decreases while the outer peaks continue to increase. At low frequency and current, a third pair of peaks appears between the two inner peaks and disappears when the frequency increases. Using a simple quasistatic model, the four-peak and six-peak structures are explained qualitatively. The variation with the current amplitude is also understood. However, accurate determination of the second harmonic signal and its frequency dependence requires a more complete model.